Isolation of styrene by azeotropic distillation with picolines and lutidines



July 27, 1948.

K. ISOLATION OF STYRENE WATER STYRENE comnnma H. ENG EL 2,445,944

BY AZEOTROPIC bISTILLATION WITH PICOLINES AND LUTIDINES Filed Jan. 22, 1946 FIRST CUT N N-STYRENE HYDROCARBONgND WATER NON STYRENE HYDRO CARBONS REMOVED 2ND cu'r STY Ema CONGENTRAI'E CfiNTAINlNG AGENT CONDENSER wag CONCENTRATE WATER INITIALLY RETURNED LATER REMOVED FRACTIONATING COLUMN PHENYLACETYLENE AZEOTRODIC AGENT OF FOLLOWNG GROUP:

INVENTOR. Earl 11 Enyel AWOW Patented Jul 'zv,

DIS TILLATION LUTIDIN ES WITH PICOLINES Karl H. Engel, Teaneck, N. J., assignor to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York Application January 22, 1946, Serial No. 642,749

23 Claims.

This invention relates to the production of substantially pure styrene or a hydrocarbon oil of high styrene content from hydrocarbon oils of relatively low styrene content.

Styrene is found in low concentration in hydrocarbon oils, particularly aromatic hydrocarbon oils, produced in such operations as coal distillation, gas production, and petroleum cracking and reforming. An aromatic hydrocarbon oil containing varying proportions of styrene in admixture with other aromatic hydrocarbons is also obtained when styrene is produced synthetically, e. g., by cracking or dehydrogenation of alkyl benzenes. From these hydrocarbon oils, styrene cuts may be obtained by fractional distillation, which cuts may contain as much as about 50% styrene, the remainder consisting chiefly of like-boiling aromatic hydrocarbons such as the xylenes and'the ethylbenzene, and sometimes also minor amounts of aliphatic and naphthenic hydrocarbons boiling close to styrene; the styrene oils thus produced generally contain phenylacetylene admixed therewith. Phenylacetylene, as is well known, interferes with proper polymerization of styrene and is, accordingly, undesirable in styrene that is to be used for the production of polymerized products, e. g., resins.

As above indicated, styrene cannot be readily separated from the close-boiling hydrocarbons, including phenylacetylene, with which it is generally associated by ordinary fractional distillation. Although some concentration of phenylacetylene in the overhead product is effected,

sufficient is left in the styrene bottoms, to give poor polymerization qualities to the styrene; moreover, the yield of monomeric styrene from such separation is poor. It has. been proposed heretofore to recover substantially pure styrene by bringing about polymerization of the styrene in the styrene oil, separating the non-styrene components from the polymerized styrene by distillation, and then cracking the polystyrene by application of heat, whereupon a substantial part of the polystyrene depolymerizes to form monomeric styrene. As this process has generally been carried out in the published prior art, the yield of monomeric styrene has been low, and a styrene product is produced in which the styrene is still admixed with close-boiling hydrocarbons.

It has also been proposed to remove phenylacetylene from a styrene oil by chemical means, for example, by treatment with an ammoniacal cuprous or silver salt; Such methods are disadvantageous for economic reasons,,both because of the cost 'of'the reagents used and the cost of the handling of the styrene oil needed to accomplish removal of the acetylenic constituents.

and reforming of petroleum oils, and styrene synthesis. I

It is another object of the invention to provide a process for the recovery of styrene from aromatic oils containing styrene and close-boiling benzene homologs such asortho-xylene, metaxylene and para-xylene.

It is a further object of this invention to provide a process in which substantially pure styrene, free from phenylacetylene, may be obtained by distillation from the usual crude styrene fractions which contain styrene in admixture with other hydrocarbons, including phenylacetylene.

I have discovered that substantially pure styrene or 'a hydrocarbon oil greatly enriched in styrene may be separated from a styrene oil containing styrene, along with hydrocarbons including aromatic hydrocarbons, not readily separable from styrene, by ordinary fractional distillation,

by carrying out fractional distillation of a mixture of such styrene oil ,and an azeotropic agent of the group consisting of the picolines, 2,6- lutidine, mixtures of the picolines, and mixtures of the picolines and 2,6-lutidine. ,Such mixtures may contain any two or all three'of the picolines, 2-picoline, 3-picoline and 4-picoline, with or without 2,6-lutidine in any desired proportion; a commercial coal tar base fraction containing '3- and 4-picolines, together with 2,6-

' lutidine, which is decidedly less costly than the pure tar bases, may be used advantageously. The styrene oil fractions subjected to azeotropic distillation may have a boiling range of from to C. at a pressure of 760 mm. of mercury.

The azeotropic agents hereinabove set forth, I have found, on addition to a styrene oil, as above described, containing other hydrocarbons besides styrene, form azeotropes of a minimum boiling type with the various hydrocarbon constituents of the oil; 1. e., when a mixture of the hydrocarbon oil and the azeotropic agent is disthe agent meadm fractionation, as described below, may be returned to the still and an amount oi agent may Bother is effected; Thevarious agents the distillate during thus be employed in the process substantially less tbanthetotal amount supplied to the still dur- 4 ing distillation; One method of; bringing about continuous recovery 01 agent from the distillate 4 duringyiractionation a'ndits return to the still is" t to. have water present "in the upper part of the fractionation column,- as more fully described below. The water may be'looked-upon as an auxiliaryazeotropic agent in this'case. it

r It agent {is added'toth'e styrene oil to be sub- .i'eeted to azeotropic fractionationin a single ad.-

, dition, ,the amount-should be regulated so'that there-will not be an. undue excess rern'ainingin I 'the still residue whem-iractionaldistillation :is

r discontinued. 11 no pli'enylacetylene is present? 1 in the'oil; the jaaeotropic distillation of styrene may be unnecessary. In that case there should be at least suflicientagent used to remove/substantially all n n-styreneihydrocarbons in the a aaeotropic distillates. Ii it is desired to separate 1 phenyiacetylene from styrene, s'uflicient agent 7 must be used to form azeotrop odistillates with Wallfhydrocarbons presenhia slight excess of agent desirable in, thislcase' 'to retain phenylacetyleneiin the stillre'sidue. If agent is added Iintermittentiy, or..if;"it is cyclically-[returned to thestilhlenough s eersnouia be'present at fall- 'ti'rne's,1ior most'efl icient-operation, to form azeo tropesjwith all hydrocarbonsiheld in the tractionatlng column during. operation or in the portion Y oithe column (if water is used as auxiliary agent) in" whichjseparation oi hydrocarbons-from each i ov r ed p fl wile-pj-,; s, r I 1 '-Thefaaeotropicdistillation i'oflthe styrene oil wh'ichi'nayg'or may not, contain; phenylacetylene' .Jw 'ith theiagent; yrithjor'without'viater as an aux- "ilia'ry; agent, may bel car'ried out either batchwiseor c0fi1 1 1, 0uSlyt-t 1111? "batchwise 1ractionation not. employing water as auxiliary agent, an anhydrous aseii i preferably used; 1 the distillate at first consistsalmostentirely of'the az'eotrppic 1 w mixture ot the agentJand non-styrene oil other than. phenylacetylenegbut.:as fractionationprm c y seeds Sand; the -y -temperature approaches the dis- .---tiliationjtemperature ofthe agent styrene aaeo-" trQD jthe styreneeontentioi the distillate gradt' uaily increasesi wever; aqueous mixtures or -j-1 the agent," which i may be available, a may be used. ,'zwhenusing such-aqueous mixtures, formost-effl-' f cient operationzol the i'ractionatingcolumn, the

v above'set-forthdiifer in that they lo'rmazeotropic' yapor mixtures containing higher, orj lower? proportions of hydrocarbons tov agrant. ."l'husgin the caseoi 2,6-lutidine, I have .1: lound the volumej'rat'io'jof'hydrocarbons to agent be aboutz'rto 1 in the vapor. In the case oi a 'B-picoIine; 4 micolinefrnixture, I have 'found the .volumeratiool hydrocarbons to. agent tobe about 3 to 2. The volume ratio of hydrocarbonsto agent V in; the, case of any other agent hereinabove set io'rth; suitable for use in" the process of my lnven'a tion', may be readily determined by preliminary .ifractlonai distillation v011a mixture;of, the agent ,in question and-hydrocarbons; and the amount- I of such agent subsequently used in an azeotropic separationprocessj-as ,herein'disclosed; may be 5m." Thepure styrene cohtaining distillat may them :ior theirstyrene content. When tlie distillate tests sufiiciently high in styrene the styrene product may. then either be withdrawn iron the still or taken as a final distillate fraction;

greater part of the styrene has been distilled over isndthetemperaturoi the still approachesthe distillation temperature '01 the agent-phenyl A acetylene azeotrope, mall proportion of'the phenylacetyle'ne may be'gintooome over with the styrene. 1 'I'hedistillation may be'stopped at this point, leaving as still residue, residual styrene containing phen'ylacetylene, which may be subjected toa separate'azeotropic.distillatidnto eii'ectg ofresidual styrene from theiplienyl- I separation acetylene. e

The course Oi the fractionation maybe foll'ov ved bytaking samples of the distillate and testing them for phenylac'etylene, Thisis doneby shaking a srn'allsample with an equal volume of5% ammoniacal silver nitrate? solution :(Tollens reagent) and noting the precipitate formed, The

distillation is advantageously-continued until the phenylacetyle'ne' contentot-the distillate rise's to 2 not more than about0.03% byweight to obtain maximum recovery of'styrene and stilllnot have present an objectionable amount of phenylacetylene; such, for-example,- as would interfere with the subsequent polymerization 0f the styrene,

Preferably, a styreneiraction is isolated, n-

taining substantially less than 03% 'phenyls acetylene. j

In continuous operation, Jthje styrene, oil and azeotropic agent may be' continuouslyointroduced into an intermediate portion of thejfractionating column. A product whose oil component'is' substanti ally pure styrene, when distilling-an oilsubg stantiaily free" oi phenylacetylene, orii-agreatly enriched styrene oilpma'y be-continuously withdrawn iromfthe' still and an azeotropic mixture of non-styrene hydrocarbon and ager'it may becon;

tinuously takenofi overhead; -,'I-his distillate. may

be condensed, the'agent separated'asides'cribed below, and the separated agent returnedftethe t'ractionating column. along}, the entering styiiene oil.

-When" distiilingan oil.containing 'phenylacety lene, after separation of hydrocarbons other than phenylacetylene, boiling close to; styrene from this. oil, a product whose oil-{component is :suh-, I stantially pure styrene maybe continuously taken oil overhead'in thefprmofanazeotropic mixture w n; the agent-and I ylaeetylene concn-a trate may be contin thdrawmirom, the

"be condensed," theagent separatedas described below, and the se'piatratedagentreturned to the fractionating column. along with I the entering styrene 011,.

- In batchwijse, distillationieniploying w 'ater as auxiliary. agent,- a'ehar ejof styrene oil which 7 may or'may not containphenylacetylene, primary agent, e.' g pico1ine,}and'water, is 'placed in'- the e still and subjectedto fractional distillation. ,In-

' stead of placing the vwatef1,'-'i'n 1thestill, 'it mayybe water obtained: Iinitheflr'st .distillates should be added directlyito-the top. of the-column The water forms az'eotropes' of the s.o.-calleci eutectic type ivith thej'hydrocarbon oils carried upward. in: the colurn'nin sazeotropic iinixtures' with the primary a ent-. Inasmuch as'tlie water-hydrocarbon .azeotropes havelower boiling points thanthe core responding primary agentihydrocargon- 'azeo hopes, the primaryfa'gent, in general, is sub'stan tially replaced by water. Applied in limited proportions, the water is completely volatilizedfrom the still charge and is eventually found in substantial proportions only in the upper part of the fractionating column and in the distillate. As the distillate is condensed, it stratiiies into a water layer and a hydrocarbon layer, generally substantially free from primary agent. The water layer may be continuously returned to the top oi the column. In th upper part'of the column, therefore, water in the liquid state, along with some condensed hydrocarbon, flows downwardly countercurrent to vapors of water. hydrocarbon and agent passing upwardly through the-column; after operation has commenced with addition of a limited amount of waterto the still, the water is driven up into the column, leaving anhydrous agent in the still charge. 1

This water flowing downwardly through the upper part ,of the column eventually is again va-' porized, its vapors displacing selectively the pri-' mary agent vapors in azeotropicmixtures with.-

hydrocarbons in the upperportlon of the column, the displaced primary agent vapors in turn being condensed and flowing downward in countercultrent to rising fresh hydrocarbon vapors. "I'hus',

the number of plates employed in the'fraction' ating column, the point at which batchwise fractionation is discontinued, and the styrene content of the hydrocarbon oil being treated. is controlled so as to give a final product of particular styrene content. I have found it advantageous when subjecting a closeout styrene fraction to azeotropic distillation, as herein described, to continue fractionation until the distillate coming over or the material remaining in the still has at least a 95% styrene content (by weight) based on the oil component ofthe material. By more exhaustive azeotropic fractionation or refractionation of a styrene-enriched oil styrene concentrations of 98% to 100% may be obtained.

If effective inhibitors are used, such as hydroquinone, phenylhydrazine, hematoxylin, or tertiary butyl catechol, higher temperatures, up-to 1 about 100 C. still temperature, and correspondwater, as well as the primary agent, are com- .'tion of the column which is'in'tended to be operated with the water-azeotrope present therein.

. -t-ained contain picoline or 2,6-lutidine, i. e. in carrying out distillation without the auxiliaryagent; water, the distillate'fractions are treated" By selecting the proper proportion of, water to; 1

column capacity, water in liquid or vapor phas is confined to' generally one-fifth of the. column space at the top, the lower four-fifths holding the primary agent as liquid or vapor, a larger column space being required for the more dimcult separation of' styrene from other hydrocarbons. As in the batchwise distillation above described, distillation is continued until a styrene product of desired purity is obtained either as still residue or final distillate fraction. V I

The distillation employing water as auxiliary azeotropic agent may also be carried out continuously by continuously introducing a mixture of the styrene oil, which may or may not contain phenylacetylene, and primary azeotropic agent into an intermediate portion of the fractionating column of a. still and column system wherein a mixture of the styrene oil and primary agent is being fractionated; water for the fractionation is introduced continuously or intermittently preferably, into the top of the column. As in the batchwise procedure above described, all or the greater part of the water needed for fractionation may be provided by continuous return of the water component of the condensed distillate to the top of the fractionating column.

When distilling an oil containing phenylacetylene, the distillation may he carried out as above described, taking oil. as distillate first the nonstyrene hydrocarbons other than phenylacetylene as an azeotropic mixture with the agent and water, and then substantially all of the styrene a an azeotropic mixture with the agent, leaving as still residue an 011- containing substantially all of the phenylacetylene or a mixture Ofthe phenylacetylene and a portion of the styrene may be left as still residue, which is later subjected to a separate azeotropic distillation, as hereinabove' described, to,separate thestyrene from the phenylacetylene.

The degree of fractionation, determined by tion.

.ingly higher vapor pressures not exceeding about 100 mm. of mercury may be maintained in the system without appreciable loss of styrene in-thev absence of such inhibitors, higher temperatures lead to increasing polymerization of the styrene.

Whencarryingout the process of my invention in such away that the oil distillate fractions obto recover the picoline or 2,6-1utidine.

oils in which they are dissolved by extraction with an aqueous solution of a mineral acid, For ex-"I I ample, the hydrocarbon solution of agentmay be agitated with a 10% to 30% solution of sulfuric or hydrochloric acid and the aqueous liquid decanted and treated with an aqueous alkali solu tion. e. g., an alkali hydroxide or alkallcarbonate solution, to spring the organic base, which forms a separate liquid layer.

Alternatively, the agent may advantageously be 5 recovered from the hydrocarbon oils in which it azeotropic agent. This may be carried out by charging the agent-hydrocarbon solution to the still with a relatively small proportion of water and subjecting the mixture to fractional distilla- The early distillate consists of azeotropic mixtures of hydrocarbon and water substantially free of agent, or azeotropic mixtures of hydrocarbon, water and relatively small proportions of agent. This distillate is condensed, whereupon it stratifles into two layers.

whereas the upper hydrocarbon layer is returned only in part, to maintain column equilibrium, the

, remainder being withdrawn. This is continued until nearly all hydrocarbon has been removedi'romthe still charge. When such a point has been reached, distillation is continued as before,

but the water layer is now withdrawn while the.

small quantity of'hydrocarbon layer is returned directly, or it may be subjected to a'simple dis tillation to obtain a colorless'product,'and this T ese agents may be recovered from the hydrocarbon The lower aqueous .layer is continuously returned to thecolumn,

t 1 the examples dieated.

Paraflinie hydrocarbonsfegiaoas' 1 in subsequent azeo tion of styrene. v

When treating a Yphenylacetylene containing oil, the. agent-may be separated fronithe still residue consisting of phenylacetylene and agent,

as hereinabove describedfin connection with rel covery of agent from distillate. containing same. As pointed out above, when a, sufiicien'tly-limited quantity or agent hasbeen used, or when water has been employed as .an auxiliary az eo-i tropic agent, sis-above; described, there may be little or no'agentremainingtin the styrene prod? uct, andin'these cases, therefore, it is only necessary to treat thenon-styrene hydrocarbon oil for removal of agent,- a

-The styrene product may subjected to a simple distillation, particularly if lt has been withdrawn as still residue rather than final distillaterraction. The styrene may also be agitated with sulfuric acid to remove minute tillate' showedfa refractive-indexer11.513 at20 amounts of color bodies; and neutralized with sodium hydroxideprior to said distillation treatment.

The accompanying drawing diagrammatically Q illustrates theembodimentiof theinvention involvin'g; the; separation of styrene. andphenyl-j' p tilling thisstyreneproduct in the presence-of 3- acetylene from s styrene oil containing Phenyl" acetylene [and involving theme of wateras auxiliary agent. It will-be understoodthe invention is notlimited to this embodiment and includes. the isolation of styrene from styrene oils tree of t phenylacetylene and with or without the use of water as auxiliary agent.

' The ,i'ollowing examples are illustrative of my invention; it will be understood the invention is.

ing 26 ignatedas styrene concentrate, L

The fractionating' sun was shamed with: 200

volume parts of the styrene concentratecontaim in; 43% of styrene and100 volume parts -01 an equal mixture of 3s and 4-picollnes, havinga mercury The mixturegwas carefully traction- V atedunder pressureoi 8 to"13 mm.joi' mercury. v v

A small amount-of paraflinic hydrocarbons m-w ent inthe styrene concentrate came oil. in 1 first cuts.- The ratio of hydrocarbon to jagent'ln 1 v t Htheiaz'eotropi'c; distillate .remained tairlylconadvantageously be K stalnt at=about 72 to 28,. decreasing gradually-as I the styrene content "or the 'distiilates increased.

C. y The still residue wasfreed" from "remaininz j picolines by extractionlwith dilute mineral acid}; dried and distilled under. reduced pressure. yield partsof styrene having ,arefractive index flof"1.54 4 at 2040. The purltyflol the styrene product was estimated at abovei.95%.. By dies hnddfpidolines, a styrene produetcontaining less; than =05% phenylacetyl'ene is, obtained as I notlimited tov these 'examples.- All percentages in p v r A styrene oil of carburetted water gjas and ooalf tar origin; having-the following :characteristiesg weight, e her s' st to Theo-11 w th 5% of'its weiehtoff sulfuric acid, 50 B ,fatroom-temperature;for;

charge ofaeld. The .oil was separated, neutral-Q Toproduce a material mhirs yrne "con tent; the washed oilwas subjectedto fraction pure styrene and oils freed ofst'yrene, '1 Distillates conta iningle'j than 21% of T one, hour; Thefspentfsulturic acid was taken-5;"

011.; and the treatment repeated with a 'i'resh;

ized with-a 'dilutesolutionof alkali, and'washed rene:were f returned-to process as too lean; other 1 tractionswere combined; Theresulting traction represented-39 volume parts of the crudejoil'. Its jtionally distilled The distillate fractlonslowin' styrenencontains .lng 3-.and4-picolines;.may be extracted-wither:

aqueous solution of minera1 acid, e." g, a. 20%; v aqueous;solution oi, sulfuric acidto recoverl the ,3- and' 'f4+p1c'olines.' The acid solution of 3- v and ;.4-picoline s may thereafter be treated with an aqueous falkalL- efig; a sodium hydroxide or dium carbonate solution, torspring the bases which: separate aslali upper 'oil layeri The fie i I vandt-flbicolineamay alsobe' separated :from the oil distillate -fractionsin which they' occur by azeotropic'distillation of'the oil with waten -as hereinabove described. Distillate fractionsd III-v .a termediate Styrene-content mayberreturnedsto I p'the stillwlthout separationof agent. distillation e e t. C ;1335119 100 volume parts oitthe styrene concentrate. 9 containing 43% styrene and '.2% 5pneny]aeety leentrated styrene in the. still..'- The styrene-ma,

taming. less -Tthan '05 tainedasdistillatel w rmer Ira tihiatedj tyr ne content was 43%;jtne; rema 'tillate Ibil had departing ing' out theLabove process without hereindes j partso! 2 ,64Ifitidine and v M described-"gin tnepreeedine. ample; In this way; the; non-styrene hldtfl carbons were selectivelv removed; leaving ja not thus; obtained contained-at le'ast 9517; .lstyg =1 iene; 5 By ,distillinzithis styrerie .produetf mime I presence oi 2;6 lutidin'e, a. styrene product 6 11-" .200vo1ume parts of styrene concentrate cong a l i -tai'ning v 43%,styrene,the sameasused {ample}, were mixed with fioq'volume partspfz' I 1 'z-picoiine. The nixturewasi carefully fraction-:1

eatedj under pressure; of ill- 14 of mercury.

- Th "',Y0 .unie ,ratio' ofoi'lt'orageiitarose rapidly g to approximately 9 to 1,: andithe'distillation was I j discontinuedwhenabout 7Q volumejpartsbl o beem collectedr: Thelbllql'feihiiih 'ingin the still at thatpoint had'astyrenea centrauour about 60%..( I

Since certaln changes may begznadein carry-g j the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a method for producinga hydrocarbon oil of high styrene content from an oil contain- 7. In a method for increasing the styrene content of an oil containing styrene and like boiling hydrocarbons, including phenylacetylene, the

steps which comprise adding to the oil an azeotent of an oil containing styrene and like-boil- 1 ing hydrocarbons, the steps which comprise adding to the oil an azeotropic agent of the group consisting of the picolines, 2,6-lutidine, mixtures of the picolines, and mixtures oi the picolines and 2,6-lutidine, subjecting this mixture to tractional distillation to separate an azeotropic mixture consisting predominantly of non-styrene hydrocarbons and azeotropic agent, and recovering from the material from which such azeotropic mixture has been separated an oil having a substantially greater styrene content than the original styrene oil,

3. In a method for increasing the styrene content or an oil containing styrene and like-boiling aromatic hydrocarbons, the steps which comprise adding a picoline to the oil, subjecting this mixture to fractional distillation to separate an azeotropic mixture consisting predominantly of non-styrene hydrocarbons and picoline, and recovering from the material from which such azeotropic mixture has been separated an oil having a substantially greater styrene content than the 7 original styrene oil.

4. In a method for increasing the styrene conadding 2,6 -lutidine to the oil, subjecting this mixture to fractional distillation to separate azeotropic mixture consisting predominantly of nonstyrene hydrocarbons and 2,6-lutidine, and recovering from the material from which such azeotropic mixture has been separated an oil having a, substantially greater styrene content than the original styrene oil.

5. In a method for increasing the styrene content oi! an oil containing styrene, and like boiling aromatic hydrocarbons, the steps which comprise adding as azeotropic agent to the oil a mixture 01' 3- and a-picolines, subjecting this mixture to fractional distillation to separate an azeotropic mixture consisting predominantly of non-styrene hydrocarbons, and said azeotropic agent, and recovering from the material from which such azeotropic mixture has been separated an oil having a substantially greater styrene content than the original styrene oil.

6. In a method for increasing the styrene content of an oil containing styrene, and like boiling aromatic hydrocarbons, the steps which comprise adding as azeotropic agent to the oil a coal tar base fraction containing 3- and 4-picolines and 2,6-lutidine, subjecting this mixture to fractional distillationto separate an azeotropic mixture consisting predominantly of non-styrene hydrocarbons and said azeotropic agent, and recovering from the material from which-such azeotropic mixture has been separated'an oil havinga substantially greater styrene content than the original styrene oil.

tropic agent 01' the group consisting of the picolines, 2,6-lutidine, mixtures of the picolines and mixtures of the picolines and 2,6-lutidine, subjecting this mixture to fractional distillation to having a substantially greater styrene content than the original styrene oil.

8. In a method for increasing the styrene content of an oil containing styrene and like boiling hydrocarbons, including phenylacetylene, the steps which comprise adding to the oil an azeotropic agent of the group consisting of the picolines, 2,6-lutidine, mixtures oi the picolines and mixtures of the picolines and 2,6-lutidine, and subjecting this mixture to fractional distillation to remove an azeotropic mixture consisting predominantly of the non-styrene hydrocarbons other than phenylacetylene and the azeotroplc agent, and leaving as still residue an oil having a substantially greater styrene content than the original styrene oil, and containing substantially all of the phenylacetylene.

9. In a methodfor increasing the styrene content of an oil containing styrene and like-boiling hydrocarbons, the step which comprises fractionally distilling a mixture of such oil and a picoline.

'10. In a method for increasing the styrene content of an 011 containing styrene and like-boiling hydrocarbons, the step which comprises Iractionally distilling a mixture of such oil and 2,6--

lutidine. 11. In a method for increasing the styrene content of an oil containing styrene and like-boiling hydrocarbons, the step which comprises fractionally distilling a mixture of such oil and a material consisting predominantly of 3- and 4-plcolines.

12. In a, method for increasing the styrene content of an oil containing styrene and like-boiling non-styrene components, the steps which comprise adding to the oil an azeotropic agent of the group consisting of the picolines, 2,6-1utidine, mixtures of the picolines and mixtures of the picolines and 2,6-1utidine, employed in amount suflicient to form azeotropes with at least a part of the non-styrene components of the'oil, subjecting this mixture to fractional distillation to separate as distillate an azeotropic mixture consisting predominantly of the azeotropic agent and nonstyrene components, and to produce as a second product a material comprising an oil having a greater styrene content than the original oil, and thereafter removing the azeotropic agent from oil fractions in which it is present.

13. In a method for production of substantially pure styrene from an industrial styrene fraction containing like-boiling non-styrene hydrocarbons, the steps which comprise carrying out continuous fractional'distillation of a mixture of ssuch styrene-fraction and an azeotropic agent of I 13- tillate. product an azeotropic mixture consisting predominantly of the azeotropic agent and nonstyrene hydrocarbons, and continuously withdrawing as residual product a material whose oil component is substantially pure styrene.

14. In a method for increasing the styrene content of an oilcontaining styrene and like-boiling non-styrene components, the step which comprises carrying out fractional distillation of a mixture of such oil and an azeotropic agent of the group consisting of the picolines, 2,6-lutidine, mixtures of the picolines and mixtures of the picolines and 2,6-lutidine, said fractional distillation being carried out in the presence of a styrene polymerization inhibitor and at a temperature of not more than 100 C.

15. In a method for increasing the styrene tures of the picolines and 2,6-lutidine, to sepacontent of an oil containing styrene and likeboiling non-styrene hydrocarbons, the steps which comprise adding an azeotropic agent of the. group consisting of the picolines, 2,6-lutidine,

mixtures of 'the picolines and mixtures of the picolines and 2,6-lutidine, to the oil, subjecting this mixture to fractional distillation in the presence of'water to take 011' as distillate an azeotropic mixture consisting predominantly of water and non-styrene hydrocarbons, and continuing the distillation until a styrene product of the desired purity is produced.

16. In a method for increasing the styrene content of an oil containing styrene and likeboiling non-styrene hydrocarbons, the steps which comprise adding an azeotropic agent of the group consisting of the picolines, 2,6-lutidine, mixtures of the picolines and mixtures of the picolines and 2,6-lutidine, to the oil, subjecting this mixture to fractional distillation in the presence of water to take oil as distillate an azeotropic mixture consisting predominantly of water and non-styrene hydrocarbons, stratifying the distillate into water and hydrocarbon layers and returning the water to the upper part of the I fractionating column, continuing fractional distillation, stratification of distillate, and return of water to the upper part of the column until the greater part of the non-styrene hydrocar lutidine to the oil, subjecting this mixture to fractional distillation to take oif as distillate an azeotropic mixture consisting predominantly of water and non-styrene hydrocarbons other than phenylacetylene, stratifying the distillate into water and hydrocarbon layers and returning the water to the upper part of the fractionating column, continuing fractional'distillation, stratification of the distillate, and return of water to the upper part of the column until the greater part of the non-styrene hydrocarbons other than phenylacetylene has been separated from the styrene oil, and thereafter withdrawing as product a styrene oil richer in styrene than the original oil, leaving as still residue an oil containing substantially all of the phenylacetylene.

18. In a method for substantially removing phenylacetylene from a styrene oil containing it.

rate as distillate product a styrene oil containing an amount of phenylacetylene irisuflicient to affect polymerization.

20. In a. method for lowering the phenylacetylene content of a styrene oil containing at least about .05% phenylacetylene, the step that comprises fractionally distilling a mixture of such oil and an azeotropic agent of the group consistingof the picolines, 2,6-lutidine, mixtures of the picolines and mixtures of the picolines and 2,6-lutidine, to separate as distillate product a styrene oil containing less than .03% phenylacetylene.

21. In the process of separating styrene from a styrene oil containing like-boiling non-styrene components involving the distillation of said oil with an azeotropic agent of the group consisting of the picolines, 2,6-lutidine, mixtures of the l picolines and mixtures of the picolines and 2,6-

lutidine to separate an azeotropic mixture of said like-boiling non-styrene components and said agent, the step which comprises distilling said mixture in the presence of water to separate as distillate an, azeotropic mixture of said nonstyrene components and water from the said agent. 7

22. In the process of separating styrene from a styrene oil containing like-boiling non-styrene aromatic hydrocarbons involving the distillation of said oil with an azeotropic agent of the group consisting of the picolines, 2,6-lutidine, mixtures of the picolines and mixtures of the picolines and 2,6-lutidine to separate as distillate an'azeotropic mixture of said like-boiling non-styrene aromatic hydrocarbons with said agent, the step which comprises distilling said mixture in the presence of water to separate an azeotropic mixture of said like-boiling non-styrene aromatic hydrocarbons and water from the said agent.

23. The process of separating a mixture of hydrocarbons and an azeotropic agent of the group consisting of the picolines, 2,6 -lutidine. mixtures of the picolines and mixtures of the picolines and 2,6-lutidine, which comprises distilling said mixture in the presence of water to distill off an azeotropic mixture of said hydrocarbons with water and thus efl'ectthe separation of said hydrocarbons from said agent.

KARL H. ENGEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

